1. Field of the Invention
This invention relates to a recording and reproducing apparatus for recording and reproducing an image signal on and from a recording medium.
2. Description of the Related Art
The known recording and reproducing apparatuses for recording and reproducing image signals on and from a recording medium such as a magnetic disc or the like include, for example, a still video apparatus.
The still video apparatus is arranged to record and reproduce an image signal in the following manner: the image signal is separated into a luminance signal and color-difference signals of two kinds. The separated signals are frequency-modulated. After that, the color-difference signals of the two kinds are alternately frequency-multiplexed with the luminance signal by switching them from one over to the other for every horizontal synchronizing (hereinafter referred to as sync) period. In other words, they are converted into a color-difference line-sequential signal for recording and reproduction.
However, the above-stated recording method of the still video apparatus has the following problems:
(1) The luminance signal (hereinafter referred to as signal Y) and the color-difference signals (hereinafter referred to as signals R-Y and B-Y) are frequency-modulated and frequency-multiplexed before recording. Therefore, if the band of the luminance signal is increased up to 7 to 8 MHz or thereabout, it would exceed a frequency band recordable on a magnetic recording medium. At present, therefore, the luminance signal band is limited to 4.5 MHz or thereabout.
(2) The frequency multiplex recording of the signal Y and the signal R-Y or B-Y after their frequency modulation tends to cause a mixed modulation distortion between the signal Y and the signal R-Y or B-Y. With the frequency modulation carrier frequency of the signal Y expressed as fy (MHz) and that of the signal R-Y or B-Y as fc (MHz), for example, a frequency distortion which is expressed as follows particularly presents a serious problem: fy - fc, fy - 2fc
(3) Further, due to a restriction imposed by the TV system, the resolution of the signal Y, i.e., the number of scanning lines, in the vertical direction is limited to 525. Then, since the signals R-Y and B-Y are frequency-multiplexed with the Y signal for recording, the color resolution in the vertical direction is also low.